MSH-1 Omni SDC

[mshilarious]

MSHilarious....You might want to take a Look at some of the Cardioid and Uni Capsules made by "Primo" ...

Thay have a few models that have much higher SNR than the Panasonic Capsules....They have at least one Cardioid model with a 78bd SNR but I can not remember the Model number but I have heard of poeple talking about these Capsules on the Mic builders Yahoo group and they have been very impressed with them......

Do you have a link? I tried a Google search, but the capsules I found don't seem to be the ones you refer to.

I have the design down so I should be able to make the PCB about 2.5cm x 1.5cm or maybe a Bit smaller and by putting the Parts on both sides of the PCB and laying the Caps on there sides I think i will be able to Fit it in a XLR

I'm not sure . . . with the new series Neutrik XLRs I am using, there is 11mm diameter x 20mm length available. The necessary caps are minimum 4mm diameter x 11mm length.

 

[Minion]

Hi, Sorry i don"t have a Link to it, It was just talked about a few times on the Mic builders Yahoo group back about 6 weeks ago...From looking on the Primo site I couldn"t fint it so maybe they are not made anymore or are a specialty item or something?

If I come across any info I will let you Know....


Cheers

 

[JasonB93117]

I just posted a link to a song that utilized the MSH-1's in a dummy head. Check it out in the mp3 mixing clinic if you like!

Thanks again mshilarious!

 

[XLR]

I just ordered a pair.

Tim

 

[scrubs]

So, when will the MSH-2 matched pairs be available?

 

[mshilarious]

So, when will the MSH-2 matched pairs be available?

That's something I've been pondering. I still want to see if I can squeeze a bit more performance out of the 2. Then I have to figure out how to roll it out. I can't decide if it will simply replace the 1, or be offered alongside it. There are several factors that I need to consider . . .

 

[scrubs]

That's something I've been pondering. I still want to see if I can squeeze a bit more performance out of the 2. Then I have to figure out how to roll it out. I can't decide if it will simply replace the 1, or be offered alongside it. There are several factors that I need to consider . . .

Well, riddle me this..I know absolutely jack about impedance matching, but you say the MSH-1 is better with a high impedance pre. I would most likely be using them with a DMP3 (which has 3 kOhms impedance on the mic input, per the manual). Should I snatch the MSH-1's or wait for the 2's?

 

[mshilarious]

Well, riddle me this..I know absolutely jack about impedance matching, but you say the MSH-1 is better with a high impedance pre. I would most likely be using them with a DMP3 (which has 3 kOhms impedance on the mic input, per the manual). Should I snatch the MSH-1's or wait for the 2's?

Definitely get the 1s unless you like to use cables longer than say 50 ft.

After thinking it over during the drive home, I am going to introduce the 2s as a replacement for the 1s, they will be called MSH-1A. I am not going to list the 1As until probably sometime next week, however anyone from this board who buys 1s until then can request 1As upon purchasing the 1s. I'm going to stick with eBay for sales since it helps me manage order quantities, so please shop there

Once the 1As are listed, there will be no more 1s--unless you make them yourself! I'm sort of sad because I like making the 1s a little better and they are cheaper and truer to the spirit of the project.

As I don't really intend to spam the board with all of this, I will remind everyone that the schematics are available above, and there are really lots of clever things that you could do. I did one custom pair that was installed in a mannequin head as a binaural pair. It's so cheap to make these, you could even wire the walls of your studio with 'em, and have different selectable room sounds I also think it would be clever as a boundary mic, if you can figure out how to mount the capsule facing down at a plate. Food for the DIYer

Also note that the capsule can be remote from the electronics, since the signal off the capsule is not super high impedance like a typical condenser. So you could cram it on a gooseneck for a cheap talkback mic, for example.

 

[Minion]

Well I made a version of your MSH-1 and a MSH-2 and on Preminalry tests they sound pretty darn good....

I use different values of some resistors and Caps and Diodes and a Different Transistor in the MSH-2 and they both work quite well...

I do notice that the MSH-2 has much higher output than the MSH-1 at least my versions of them did...

The only thing I did differantly with the MSH-1 is I use 6.8k resistors instead of the 7.5k ones and used a 2.4v zener but it works fine...

In the version of the MSH-2 I did i used 750r resistors instead of the 1k and 4.3k instead of 4.5 and I use 15uf caps instead of the 22uf as I didn"t have any 22uF and I used a 5.4v Zener and a very low noise NPN in the BC550C and It has a Lot more output than the First version, I don"t know if it is the Components I used or if it is part of the design......

After I do some more tests i will post a review and i might try a few different mods and see if I can get different sounds.....

ThanXX

 

[tmix]

Definitely get the 1s unless you like to use cables longer than say 50 ft.

After thinking it over during the drive home, I am going to introduce the 2s as a replacement for the 1s, they will be called MSH-1A. I am not going to list the 1As until probably sometime next week, however anyone from this board who buys 1s until then can request 1As upon purchasing the 1s. I'm going to stick with eBay for sales since it helps me manage order quantities, so please shop there

MS,
I just ordered a pair! Should I request the 1a? Whichever variety would be the quietest is my preference.
My ebay name is tmix.

Tom

 

[mshilarious]

The only thing I did differantly with the MSH-1 is I use 6.8k resistors instead of the 7.5k ones and used a 2.4v zener but it works fine...

Little difference there, the zener limits the supply voltage anyway. That is by design, it keeps the current draw down when the preamp input impedance drops.

In the version of the MSH-2 I did i used 750r resistors instead of the 1k and 4.3k instead of 4.5 and I use 15uf caps instead of the 22uf as I didn"t have any 22uF and I used a 5.4v Zener and a very low noise NPN in the BC550C and It has a Lot more output than the First version, I don"t know if it is the Components I used or if it is part of the design......

The only way the output could be different is probably the capsule (they vary by up to 2dB), or if you are using a low input impedance. At 600 ohms the difference in output between the 1 and 2 is something like 6dB.

In the 2, the zener doesn't really do that much other than equalize the performance with low phantom supplies. I'm not sure what your exact voltage would be with your resistor values, but I think it's less than 5.4V.

The value of the caps only affects (very) low frequency response, 15uF is probably fine there. 22uF is the biggest cap that can fit inside an XLR connector, so that's why I used it.

 

[mshilarious]

MS,
I just ordered a pair! Should I request the 1a? Whichever variety would be the quietest is my preference.
My ebay name is tmix.

Tom

The 1s should be slightly quieter as they don't have the added transistor, but the difference is something like 0.3dB, at least in theory . . .

 

[scrubs]

Alright, I'm going with the MSH-1. But if I see an MSH-1 vs. MSH-1a poll and everybody says the 1a is better, I'm going to be steamed.

 

[tmix]

That is fine. I'll just stick with the 1's.
I can always buy a second pair later if I want the higher output.

Thanks

Tom (tmix)

 

[JonSinger]

Hi. Sorry about the delay. The performances went quite well, but they were rather exhausting, and I've been kinda slow getting back in gear.

To return (at least briefly) to the issue of modifying the capsules: I notice that you say you don't get any performance increase. I asked Siegfried Linkwitz whether he had measured distortion on the unmodded and modded WM-61A, and whether he saw the same kind of issue at high SPLs with unmodified capsules that he had previously seen with the WM-60AY; he said yes. Any idea why the difference?

I was also advised (by someone else) that because the casing is merely crimped onto the circuiboard [this is true -- I checked a couple of them with a stereomicroscope] they have a tendency to be a db or two down at 20 Hz, and that the back side should be sealed somehow (I'm using epoxy) to bring them up to spec. That make sense to you? I can't check it because I have no test equipment to speak of and no calibrated sources.

Either way, MANY thanks for the schematics and all the helpful information!!
jon

 

[mshilarious]

To return (at least briefly) to the issue of modifying the capsules: I notice that you say you don't get any performance increase. I asked Siegfried Linkwitz whether he had measured distortion on the unmodded and modded WM-61A, and whether he saw the same kind of issue at high SPLs with unmodified capsules that he had previously seen with the WM-60AY; he said yes. Any idea why the difference?

No, not really. Some of the stuff on the Linkwitz site confuses me. I haven't been able to improve distortion at high SPLs by increasing supply voltage, for example. Of course the 2mA current limit of WM61A certainly doesn't help my model 1 any there. I am going to give it one final try tomorrow, when I decide on the final 1A (formerly 2) model. I really thought I should get some more SPLs there.

Regarding the page here:

http://www.linkwitzlab.com/images/graphics/microph1.gif

The "conventional " hookup is clearly deficient, Linkwitz is right on. I use a higher supply voltage than 1.5V, and my capsule is floating, so there is a source (and drain) resistor. However, I don't get up to the 9V level in the "source follower" diagrams. I can't really squeeze a 9V supply out of my design without making it substantially more complex. So it may be I never approach the SPL handling of the Linkwitz mic. I will know more tomorrow after another round of testing--I do it the hard way, live in my studio, wearing earmuffs

If you pull the zener from model 1A/2, you get something like 4V across the capsule. I've tried that before with unsatisfactory results at low input impedances. Could be worth it if you don't use low impedance pres. However, removing the zener from model 1 will yield very bad results at any input impedance below 2K or so.

I was also advised (by someone else) that because the casing is merely crimped onto the circuiboard [this is true -- I checked a couple of them with a stereomicroscope] they have a tendency to be a db or two down at 20 Hz, and that the back side should be sealed somehow (I'm using epoxy) to bring them up to spec. That make sense to you? I can't check it because I have no test equipment to speak of and no calibrated sources.

I seal the backplates with cyanoacrylate glue; I had heard the bit about loss of low frequency response, but I also like it just to strengthen the leads and capsule assembly a bit.

I have never done a controlled test of sealed vs. unsealed, but one thing you have to understand is how dramatically these capsules vary in low bass response. It's a LOT more than the 2dB advertised for the whole spectrum. Indeed, usually the capsules are within 1dB of each other across the whole range, but when you get down to 20Hz, it can be 6dB or more, even for capsules that otherwise match perfectly. It does make matching mics a challenge.

 

[Minion]

Hi, I was just wondering if you could Raise the Voltage going to the Capsule by lowering the Values of some of the Resistors (7.5k in v1 and 4.5 in V2) because isn"t it the Resistors in the design which lowers the Voltage??

If you use a 1w 1.6K resistor it should take the 48v and drop it to 9v and supply 25mA of current, at least those are the numbers I get.......

I might be totally wrong but with the limited knowlege I have this is what i come up with....

Cheers

 

[mshilarious]

Hi, I was just wondering if you could Raise the Voltage going to the Capsule by lowering the Values of some of the Resistors (7.5k in v1 and 4.5 in V2) because isn"t it the Resistors in the design which lowers the Voltage??

Yes. Let's take v1 and v2 separately.

Those resistors also act as a load on the capsule. Therefore if they are dropped too low, in combination with the parallel preamp input impedance, the load on the capsule can get excessive. When I designed v1, I had two goals: reasonable, consistent performance down to 1000 ohm input impedance as well as 18V phantom. Thus I kept those resistors a little large, and used a small value Zener, so that the mic would provide that consistency. If you are designing for yourself, and have high input impedance pres, and only use 48V phantom, you can drop the resistor values and remove the zener. But be careful! The FET in the capsule can only manage 2mA.

You will find circuits on internet for these type of capsules that go the other way and use 22K/2.2K for those resistors rather than my 7.5K/1K. That will actually yield higher output than my mic, but as you start to drop input impedance, the output plummets fast.

In v2 you have more wiggle room to change values and increase capsule voltage, but with a single transistor design, there are still limits.

Keep in mind this is far from the best possible circuit that could be made using WM61A. It's more like "the best possible circuit that can be made using WM61A that will fit in an XLR connector and I can sell for $20 and still feed my children"

If you use a 1w 1.6K resistor it should take the 48v and drop it to 9v and supply 25mA of current, at least those are the numbers I get.......

First off you shouldn't ever need 1W resistors when dealing with phantom, there just isn't that much power available. That is because the 48V comes through 6.8K resistors, so max current is only 14mA.

But again, unless you buffer the capsule with a high impedance (say 10K or so), you don't want to hit the capsule with 9V, because it can only manage 2mA current.

 

[MadAudio]

Sorry to interrupt the tech talk, but here's a track to listen to. I played the drums as well as doing all the engineering. I used a pair of MSH-1s as room mics in addition to my usual drum mic set-up.

Note - this is not quite the final mix.

 

[mshilarious]

Here it is folks

The MSH-1A design is final. A few changes from the MSH-2 published above. Basically I gave up some stability for lower distortion and higher SPL handling. The resistor values changed, and I omitted the zener. A zener still isn't a bad idea, I would go with Minion's 5.4V, that should be slightly less than the unregulated supply which I test at 6V.

Various stats between the three versions:

THD 94dB SPL @ 1% THD Sens 1500 ohms 600 ohms 150 ohms
1 0.25% 110dB -39 -46 -53
2 0.3% 110dB -39 -41 -45
1A 0.15% 116dB -39 -42 -47

Haven't tested noise yet, but I suspect it is roughly the same for all three.

Incidentially, the 1A tests at almost exactly the same as my Apex 220, so I must have stumbled pretty close to that circuit (although I don't know what the Apex circuit is).

Just for grins, here is my test of a Shure KSM141:

141 0.12% 126dB @ 0.7% -37 -39 -43

So don't throw away your good mics just yet